Process of removing phenols from mineral oils



Aug. s, 1940.

A. c. BYRNs 2,210,542 PROCESS OF REMOVING PHENOLS FROM MINERAL'OILSFiled Dec. lO, 1938 Spider for cz'rcuiah'ng Causz'c INVENTOR. lva C.Byrns' A TTORNEY.

Patented Aug. 6, 1946 rnocEss or nEMovING rnENoLs rnoM MINERAL olLs AlvaC. Byrns, Los Angeles, Calif., assigner to Union Oil Company ofCalifornia, Los Angeles, Calif., a corporation of California vApplication December 10, 1938, Serial No. 244,964

4 Claims.

This invention relates to a method of removing impurities from'hydrocarbon fractions. More specifically it relates to a method of`removing phenols or phenol-like bodies from hydrocarbon 5 oilfractions.

In the preparation of certain low-boiling solvents from hydrocarbon oilfractions, it is customary to mix the fraction with a selective solvent,such as sulphur dioxide, aniline, nitrobenl zene, furfural,l phenol ordichloroethylether in order to separate the more parainic from the lessparainic material. The phase which remains undissolved in the solvent iscomposed chiefly of the more parailnic fractions of the oil. The oilswhich are dissolved in the solvent and which make up the extract phaseare the relatively non-parafnic oil fractions contained in the originaloil. After the two phases formed by the above extraction are decantedaway from each other, they are separated from the solvent by fractionaldistillation.

The less parafnic oil fractions recovered from the extract phase areusually rich in hydrocarbons off an aromatic nature and for that reason25 may be substituted for many uses for which benzol, or its homologues,are employed. I1n particular, the low boiling aromatic fractionsrecovered from petroleum, and especially from asphalt base petroleum,are valuable as solvents and thinners in the preparation of paints andlacquers providing they have been sumciently rened to remove impuritieswhich would impair the drying qualities of said paints and lacquers.

Many of the low boiling hydrocarbon fractions 35 produced from asphaltbase crudes are unsuitable as solvents and thinners because they containimpurities, such as phenols and phenol-like bodies, which hinder thedrying properties of paints or lacquers in which said hydrocarbonfractions have been incorporated. These phenols or phenolic materialshave also been found to impair the drying qualities of drying oils, suchas are present in paint, and to which drying accelera- 45 tors, such ascobalt salts, have been added.

Therefore, in order to produce premium low boiling solvents and thinnersfrom asphalt base crude oils, it is important that the content ofphenolic bodies in the hydrocarbon fractions be reduced 50 to a'pointwhere the drying qualities of the paints and lacquers in which they havebeen incorporated are not impaired.

In the present renery production of solvents from relatively aromatichydrocarbon fractions containing phenolic materials, it is customary to5 wash the solvent with a strong solution of caustic soda whichmaterially aids in lowering the phenolic content of the oil. However, itis not practicable to remove all or substantially all of the phenolsfrom such hydrocarbon fractions by caustic soda alone since thedistribution ratio of said phenolic materials between the caustic sodaand hydrocarbon phases is such that excessively large volumes of causticsoda solution would be required and the caustic soda would be veryineflciently used. 5

I havediscovered that the phenols and phenolic bodies may be removedfrom petroleum fractions by a method in which relatively small amountsof caustic soda or other alkali are used for the treatment. According tomy process, the hydrocarbon fraction containing the said phenols andphenol-like compounds is commingled with the aqueous caustic sodasolution. During this treatment, a portion of the phenolic compoundsbecomes dissolved in the caustic soda solution which is subsequentlyseparated from the treated hydrocarbon phase and` admixed with anoxidizing agent such as potassium permanganate, hydro-u gen peroxide,potassium dichromate, etc. The 39 oxidizing agent converts the phenolsand phenolic bodies into compounds which are highly soluble in thecaustic soda and relatively insoluble in the hydrocarbon fraction. Thetreated caustic soda :is then again mixed with the hydrocarbon oilfraction in order to remove further'quantities of the said phenoliccompounds. The cycle employed is therefore as follows:

The hydrocarbon oil fraction, containing phenolic bodies, is rst treatedwith an alkali thereby dissolving a portion of the phenolic bodies. Thealkali solution is then subjected to an oxidation treatment to convertthe said phenolic materials present in the caustic into compounds ofrelatively greater solubility in the alkali solution and of relativelyless solubility in the hydrocarbon fraction, after which the treatedalkali solution is further contacted with the hydrocarbon fraction forfurther removal of phenolic materials.4

It is, therefore, an object of my invention to 50 remove phenols andphenolic materials from hyalkali for further treatment of the partiallyde phenolated oil.

My invention can be more fully appreciated by reference to the figure.In the drawing, I represents a treater, I9 is a supply tank for thecaustic treating solution and I4 is a source of supply for the oxidizingagent. In carrying out the inven` tion according to my process, oil isintroduced into the treater I through line I5 and valve I6, alkali isintroduced into the top of the treater I through spider 9 from tank I9through valve 20, line ZI, pump 22 and line 5. Aiter the alkali haspassed downward through the body of oil in treater I, it accumulates inthe bottom cone of this treater and is withdrawn through line 2, valve 3and sent by means of pump 4 into line 5 into agitator 23 where it isthoroughly mixed with an oxidizing agent Withdrawn from tank I4 throughline I3 and passed by means of pump I2 through valve Y II and line I0 toline 5 and thence into agitator 23. The mixture in agitator 23 thenpasses through valve 6 and line 5 to spider 9 where it is again used tocontact the oilin treater I. It is preferable that line 5 be of suchv alength, which Will be dependent von the rate of flow through the lineand the character of the particular oxidizing agent, that surlicienttime will have been allowed for the substantially complete oxidation ofthe phenolic materials present in the alkali solution before the latteris returned through spider 9 for further treatment of the hydrocarbonphase.

After a. thorough dephenolizing treatment, the treated oil in treater Iis withdrawn through valve I8 and line I1. @Line 1, containing valve 8 iis a drain line employed for observation of the circulating caustic.

As explained above, the oxidizing agent lemployed in this system vmay'be potassium permanganate, hydrogen peroxide or potassium dichromateor, in fact, any other oxidizing agent color.

Furthermore, under some circumstances, it may be desirable to filter thealkali solution after it has been treated with thepotasslum permanganateand prior to its introduction into treater I in order to remove anyprecipitated manganese dioxide present in the alkali which wouldcontaminate the treated oil if permitted to ilow into the treater. Themanganese dioxide present in the alkali may be removed by centrifuglngor ltering the alkali after treatment with the potassium permanganate,and just prior to its introduction into treater I.

As a. specific example of carrying out my invention, topped keroseneextract, having a boiling range of approximately 345 F. to 440 F.,

produced by the extraction of kerosene distillate with liquid sulphur`dioxide according to the well known Edeleanu process and subsequentdistillate, and containing about 3000 parts per million (p. p. m.) ofphenols (by method TM-235) is treated as follows:

This extract fraction is treated first with ten pounds of 98% sulphuricacid per barrel of extract in the usual manner employed in acid-treatingoil. This treatment reduces the phenol content of the extract to about1500 p. p. m. The acid-treated extract is then subjected to treatmentwith three washes of 1% caustic soda solution using ,25% by volume ofthe 1% caustic solution for each wash. This treatment with caus- Vticlowers the phenol content of the hydrocarbon fraction to about r p. p.m.

The partially treated stock is then contacted with 10% by volume of a 2%solution of caustic soda. The caustic soda withdrawn from this treatmentis then treated with suiiicient saturated solution of potassiumpermanganate to convert the phenols present in the caustic soda intocompounds which are relatively more soluble in aqueous phase. Thetreated caustic soda is then returned again to the treater where it iscontacted with the hydrocarbon phase for further removal of the phenolspresent. After the second treatment, the caustic soda is again treatedrwith a further quantity of potassium permanganate and again returned totreater I for retreatment of the oil.4 This cycle is continuouslymaintained until the phenol content of the oil in the treater is reducedto the desired value. The consumption of potassium perrnanganate in theoxidation of the phenols present in the caustic soda is estimated to beabout four times the initial phenol content of the solvent. For acontent 'of 750 p. p. m. of phenols in the hydrocarbon, 0.3%- opotassium permanganate would be required or about 5% of a 6% solution ofpotassium permanganate. This represents approximately one pound ofpotassium permanganate per barrel of the particular solvent stock.

Atilled tothe desired boiling point.

As a second example, two gallons of topped kerosene extract having aboiling range between B30-440 F. and containing about 2240 p. p. m. ofphenols as determined by method TM-235, were treated with ten pounds of98% sulphuric acid per barrel, agitated iive minutes, allowed to settlethirty minutes, decanted, filtered 'and washed with 10% by volume of 1%caustic soda. The resulting crude solvent contained 1300 p. p. m. ofphenols.

The crude solvent was then washed with 10% by volume of 2% caustic soda.The caustic soda from this treatment was mixed with suilcieut saturatedsolution of potassium permanganate to produce a green manganate colorwhich persisted throughout fifteen minutes of agitation of the oil withthe caustic soda. The consumption of potassium permanganate by thistreatment was 1.6 pounds per barrel of the oil. The

-oil dephenolated by this method was found to contain 19 p. p. m. of thephenols. A heart cut 18 to 81% by volume of the total distillate) wasobtained by distillation and found to contain about 25 p. p. m. ofphenols. The color of this oil was '22 Saybolt and was improved to 24Saybolt on treatment with 1 pound coenite clay Gravity, 3A. P. I. at 60F 31.1 Engler distillation, F.:

Initial boiling point 372 i 10% 379 20% 383 386 388 390 393 396 400 405f 410 Dry i 415 Maximum 418 Recovery, per cent by volume 98.5 Phenols,4method A'TM-235, p. p. m 25 Aniline point, modied 50/50, C 32.2Aromatics (solubility in 99% H3S04), per

cent by volume 66 Flash point, Tag.,-"?I 149 Color, Saybnlt I +24 Copperstrip corrosion 'at 360 F Pass pends on the formation of lyellow colorednitroso nal In the two foregoing examples I have described the treatmentof the mineral oil with weak caustic. solutions containing 1% and 2% ofsodium hydroxide, respectively. I find it desirable to use weak causticbecause it has a higher solubility for sodium lphenolate than strongcaustic or strong alkali solutions. I iind that in most instances acaustic soda solution containing the 1 to2% sodium hydroxide is highlysatisfactory in the process,

however, I may use caustic soda solutions containing, for example, 10%sodium hydroxide or even higher.- It is' also to be understood thatwhile I have described the use of sodium hydroxide in my process, othercaustic alkalies, such as potassium hydroxide, may also be used..

In the two foregoing examples, I have described the removal of phenolsfrom oils which have been given a previous acid treatment. It is 4to beunn 45 derstood, however, that the process is not limited to the removalof phenols from acid-treated oils, since the process is readily adaptedto the removal of .phenols from oils which have been given noprevioustreatment by acid, or by any othertreating agents.'

Throughout the specication, I have referred to the phenol content bothprior to treatment and after treatment. The. method which I haveemployed to determinethe phenol content of these oils is designated inthis specification as TNI-235, and has been developed by the du PontCompany to determine the presence and amount of such phenolic compoundsas phenol, cresol, guaiacol and related materials in hydrocarbonsolvents. The method is based on an article by Stoughton, J. Biol.Chem., 115,293 (1936). The method de- 'compounds by treatment of anacetic acid solution of the phenol with nitric and sulphuric acid. Theintensity of the color produced in alkaline solution is compared with astandard (ptertiary butyl phenol) prepared in the same way.

A 25 cc. sample of the hydrocarbon solvent is treated ina separatoryfunnel in several successive extractions with 25 cc. of 0.2 normal KOH,treating each extraction as directed below, until further extractionsyield no color.

Each extraction is placed in a 100 cc. volumetric ilask, neutralizedwith 25 cc. of 0.2 normal H2SO4, and then diluted to the 100 cc. markwith glacial acetic acid. To 50 cc. of this solution placed in a cc.Erlenmeyer flask is added 6 drops of concentrated HzS04 and 6 drops ofconcentrated HNOs. The mixture is then heated on a steam `bath until apale yellow color develops and reaches a maximum (5-30 min.). Theremaining 50 cc. is treated in like manner as a check. Cool, thencarefully make slightly alkaline with concentrated ammonium hydroxide(about 35 cc.) Dilute to 100 cc. with water and compare in a calorimeterwith a standard prepared as iollows:

Place 25 cc. of a standard phenol solution, prepared by dissolvingfreshly distilled phenol or p-tertiary butyl phenol in distilled water,and containing 60 parts per mil1ion, in a 100 cc. volumetric flask. Add25 cc. of distilled water and dilute to the mark with glacial aceticacid. To 55 cc. of this solution add 6 drops of concentrated H2SO4 and 6drops of concentrated HNOa. Heat on a'steam bath, neutralize and, diluteto 100 cc. as described above. f

The phenol content of the sample in parts per million is equal to thecalorimeter reading of the standard multiplied by the colorimeterreading of the sample divided by the phenol content of the standard inparts per million.

The calculated phenol contents of each of the several extractions areadded to give the total phenol content of the solvent, expressed asparts per million of the particular phenol used as a standard. i

'I'he method described in conjunction with the sketch is essentially abatch process. It is to be understood that I do not wish to limit myselfby the process shown in `this sketch since, in this sketch, I may carryout the process by feeding the oil to be treated into the bottom of atreating column and then feed the alkali into the top of the treatingcolumn, withdraw treated oil from th'e top of this column and withdrawalkali, containing phenols, from the bottom of the column, which may besubjected to the oxidizing treatment described above in cpnjunction withthe batch process and then returned to the treating cycle.

I claim: 5

1. A process of'removing phenols from mineral oil which comprisesagitating said oil with an alkali containing an oxidizing agent selectedfrom the class consisting of potassium permanganate, potassiumdichromate and hydrogen peroxide to convert the phenols into compoundswhich are relatively more soluble in said alkali solution and separatingthe mineral oil from the alkali.

2. A process of removing phenols from mineral oil which comprisesagitating said oil with analkali containing potassium permanganate toconvert the phenols into compounds which are f soluble in said alkalisolution and separating theV oxidizing agent selected from the classconsisting of potassium permanganate, potassium dichromate and hydrogenperoxide.

4. In the process of treating mineral oil for the removal of phenolswhich process comprises contacting said oil' with an aqueous alkalisolution uA yaqueous alkali than said phenolates and` then to convertthe plieno'ls present in said oil into treating mineral oil containingphenols'with said phenolates, removing the aqueous alkali solutionalkali which has been Atreatedv with said agent,

containing phenolates dissolved therein from the the step of treatingsaid aqueous alkali solution 4mineral oil, contacting the aqueous alkalisolucontaining said phenolates with an oxidizing` tion containingdissolved phenolates with an oxiagent selected from the class consistingofV potasdizing agent to convert said phenolates into comsiumpermanganate, potassium dichromate and pounds which are relatively moresoluble in said Y hydrogen'peroxide. f

' `ALVA` C. BYRNS.

